There are various reasons and applications for configuring an opened and closable set of channels through which gas or fluids flow. The ability to allow gas and other fluid flow through such a set of channels can be used for mechanical purposes such as locomotive forces, or for maintaining gas/fluid flows such as for lab-on-a-chip applications, or for informational purposes such as conveying a representation of information or data. Increasingly, there is a desire to implement such systems in a closely spaced array to obtain a higher density of gas channels within a smaller space or volume. High density arrays can provide more precise data and information storage and representation, as well as greater capacity for mechanical or other uses. While not meant as limiting, it has been observed that an array of valves to control openings, having a diameter or width of about 2 mm, would be within the definition of a microvalve array. Because the previous statement is not meant as limiting as to dimension or scale of embodiments herein, the words microvalve and valve generally are used interchangeably throughout these teachings.
In the context of pneumatic valve arrays and similar systems that employ the movement gas or air flowing under pressure, the gas channels whose open/closed states are controlled by microvalves are generally placed into communication with an air reservoir and a pump or a vacuum. In certain settings, it is desirable to have gas flow channels that can be controlled so they will either allow or not allow the passage of discrete bursts of air or gas. This would also be true for fluid flows such as liquids. While the current description is expressed primarily in terms of pneumatic flow control, the principles and teachings would apply to liquid as well as pneumatic flows.
Bilayer films having a compressive layer and a tensile layer that causes the film to coil and retract to open a pathway for light or matter have been used as actuators for various kinds of systems. However, the ability to selectively actuate a particular valve, or to do so partially, helps realize some additional benefits with these systems, for example by offering a more dynamic and precise pneumatic system. Consider a microvalve array that is meant to represent visual information for the blind. However, instead of visual stimuli the information is represented by tactile cues consisting of periodic air bursts and gas flows that can be sensed by a user's finger, and whose intensity, duration, and frequency act in the same way that gray scale images serve the sighted portion of the population. In that setting, one can appreciate the desire to maximize the density of gas flow channels to provide enhanced resolution of the represented image. And with the need to make devices ever smaller, the larger in number a microvalve array can be, the greater the possibilities allowing for a variety of images and image details to be created. As well, such approaches to representing information for the visually impaired can go far in overcoming the inherent educational challenge when it comes to students' ability to learn visual subject matter such as geometry and calculus.
With some bilayer film systems, electrodes are used such that the coiling or unrolling of the bilayer film (i.e., whether a valve is open in the coiled state, or closed in the unrolled state) is controlled by applying voltage to the system. When voltage is controlled at each valve separately, it enables the valves to be individually controlled. Even so, various problems are sometimes encountered with these systems. For example, one potential problem may occur as the bilayer releases and unrolls over many cycles, such that the outer edges existing further from the actuator's coiled center might curl upward along the unconstrained edges and corners of the bilayer. A number of negative results follows from that type of curling, including lack of complete valve closure. Accordingly, better supported, more reliable, more consistent, and more efficient actuators are needed for a variety of applications, including pneumatic manifolds for industry, for use with fluidic arrays in lab-on-a-chip applications, and for tactile tablets for the visually impaired, to name only a few.